The present invention relates to tactile transducers used to produce ambient vibrations in concert with audio loudspeakers and enhance the bass sound experienced. Scientifically, a tactile transducer or “bass shaker” is a device designed to allow people in the surrounding ambient to feel as well as hear low bass frequencies by transmitting low-frequency vibrations into various surfaces. Tactile transducers may augment or in some cases substitute for a subwoofer. Typically, a bass shaker is meant to be firmly attached to some surface such as a seat, couch or floor. The shaker houses a small weight that is driven by a voice coil similar to those found in dynamic loudspeakers. The voice coil is driven by a low-frequency audio signal from an amplifier; common shakers typically handle 25 to 50 watts of amplifier power. The voice coil exerts force on both the weight and the body of the shaker, with the latter forces being transmitted into the mounting surface. Tactile transducers may be used in a home theater, a commercial movie theater, or for special effects in an arcade game, amusement park ride or other application.
An early bass shaker is described in U.S. Pat. No. 5,424,592 to Bluen et al. In that patent, the named inventors described an improved electromagnetic actuator that included a first assembly, a second assembly disposed for relative movement with respect to the first assembly and at least a first flexure interconnecting the first assembly and the second assembly. The first assembly included a core having a first magnetic pole of a first polarity and a second magnetic pole of a second polarity. The second assembly included an electrical current conductive coil having a first coil portion and a second coil portion. The first magnetic pole is in a facing relationship to the first coil portion and the second magnetic pole is in a facing relationship to the second coil portion. The first coil portion and the second coil portion are arranged so that an electrical current in the coil develops additive flux current cross products at each of the first coil portion and the second coil portion. One of the first assembly and the second assembly includes a magnetic flux return path between the first coil portion and the second coil portion.
Other tactile transducers of similar and different technologies have been disclosed over the years. With time, however, certain limitations became apparent with prior art bass shakers that prevented as robust and high quality sound and vibrational output as could otherwise be achieved. The present invention addresses at least some of those limitations.